The invention deals with compounds having activity as phospholipase A.sub.2 (PLA.sub.2) inhibitors. PLA.sub.2 is a calcium-dependent enzyme which cleaves the sn-2 acyl bond of phospholipids to yield arachidonic acid and a lysophospholipid (H. Van den Bosch et al. in Biochim. Biophys. Acta 1980, 604, 191). Both products of this reaction can serve as starting points for the biosynthesis of inflammatory mediators. Once released, arachidonic acid is rapidly metabolized by enzymes such as cyclooxygenase and lipoxygenases to give prostaglandins and leukotrienes, well-known mediators of inflammation (P. Davies and D. E. MacIntyre in "Inflammation: Basic Principles and Clinical Correlates," 2nd Ed., J. I. Gallin, I. M. Goldstein, and R. Snyderman, Eds., Raven Press, Ltd.: New York, 1992; Chapter 7; B. K. Lam and K. F. Austen in "Inflammation: Basic Principles and Clinical Correlates," 2nd Ed., J. I. Gallin, I. M. Goldstein, and R. Snyderman, Eds., Raven Press, Ltd.: New York, 1992; Chapter 8). Lysophospholipids can be utilized by certain cell types to produce platelet-activating factor (PAF), another potent inflammatory mediator (G. A. Zimmerman, S. M. Prescott, and T. M. Mcintyre in "Inflammation: Basic Principles and Clinical Correlates," 2nd Ed., J. I. Gallin, I. M. Goldstein, and R. Snyderman, Eds., Raven Press, Ltd.: New York, 1992; Chapter 9). The role of PLA.sub.2 in inflammatory diseases has been described (P. Vadas and W. Pruzanski in Laboratory Investigation, 1986, 55, 391-404; W. Pruzanski, E. Bogoch, M. Wloch, and P. Vadas in Journal of Rheumatology, 1991, 18, 117-119; W. Pruzanski, K. Scott, G. Smith, I. Rajkovic, E. Stefanski, and P. Vadas in Inflammation, 1992, 16, 451-457; W. Pruzanski, D. W. Wilmore, A. Suffredini, G. D. Martich, A. G. D. Hoffman, J. L. Browning, E. Stefanski, B. Sternby, and P. Vadas in Inflammation, 1992, 16, 561-570; J. M. Gronroos and T. J. Nevalainen in Digestion, 1992, 52, 232-236). Since PLA.sub.2 is the critical enzyme in the pathway leading to release of prostaglandins and leukotrienes and PAF, inhibition of this enzyme is a rational approach to prevention, elimination, or amelioration of inflammation.
Compounds having similar activity are disclosed in U.S. Pat. No. 5,141,959, the disclosure of which is hereby incorporated by reference. That patent discloses compounds of structure A: ##STR1## wherein R.sup.a is CH.dbd.CY--C(CH.sub.3)=CHX, wherein X and Y are different and are selected from COOR.sup.b and ##STR2## groups in which R.sup.b and R.sup.c independently are H or C.sub.1-6 alkyl.